VS Stalling and spluttering

[steino]

Hi all! Had a search through the threads about stalling probs for my V6 VSII, but not having much luck.

Got an error Code 76 - Air/Fuel ratio variation between left and right banks. Throttle body has been cleaned, as has IAC, just gone through a full service with both Ox sens replaced, and they said they "THINK" (I hate when they say that:bang: ) that an injector might be leaking. She's running extremely rich and stalls at the lights while trying to take off and splutters while driving. Buggered Air Flow Sensor, or CAS sensor? Any suggestions other than sell the damn thing? *I shouldn't complain too much, oh how I do love her...*

 

[fixedit]

I'm in the same boat with mine. Its just been sitting in the front yard since it got towed last Saturday. Hoping someone who has had this problem and fixed it will tell us how. If not I'm just gunna chuck it. Don't feel like spending $1000 just to find out when I can get another one that works for the same money.

 

[Michelson4301]

could be injectors, or leaking exhaust manifold ?? hope this helps
reco injectors of ebay go for $120 a set

 

[digisol]

If the work fixed the fault code then;

If the IAC valve was cleaned it's likely that you missed the bit in the manual about NOT spraying cleaner into the IAC hole, that said most still do but keep the valve side up when cleaning it.

Carb cleaner will make the valve stick as it dries the hole out, a "small" squirt of WD will free up the valve, essentially a small piston.

Did mine some time back and when the WD "or whatever" squirt was applied into the hole the idle dropped another 150 rpm.

All that aside I just had similar dramas, with 24 lit / 100 kms, bought a dirty batch of fuel, changed the filter, now down to just over 6 lit / 100 kms.

 

[steino]

Alrighty, Got ebay injectors installed, changed the fuel filter, and checked that the exhaust manifold isn't leaking. Not much improvement yet. The stalling seems to only happen now when I brake suddenly. She idles a little rough sometimes, and is still running extremely rich. The weird thing is the problem comes and goes (comes a little too often though!) Any ideas?? Might have to bite the bullet and get Holden to look at it.

 

[cacaman]

I had the exact same prob on my Vr and it happened soon after i put pace maker exctractors with full exhust system and highflow cat on mine but its fairly easy to fix. I replaced my MAP sensor since it wassent working properly and reading the 02 sensors really rich at about 7% during cruise. I suggest replace the MAP sensor then reset the ECU by disconnection the battery leads.
Also if u you do have an exhaust system with extractors and cat back system what tends to happen is there is not enough back pressure in the system because there is too much flow, the 02 sensors need some back pressure to properly read the air ratio in the exhaust, if not it cant read it properly and wont lean out and will constantly become richer.
But give the MAP sensor a go and make sure u reset the ECU

 

[Michelson4301]

Have you tried blocking the hose from the manifold-to-brake booster ? when they wear out a small hole usually develops that can allow unmetered air to be sucked in all the time or even on brake applications only.

 

[Dragz]

whats a map sensor and how much would it cost for my VR commodore?

 

[digisol]

Now U know more than most.

A MAP (Manifold Absolute Pressure) sensor is a common item on nearly all fuel injected engines today and can be
used in a number of different ways especially when used with a MoTeC ECU.
Absolute pressure is a pressure measured against total vacuum (zero pressure). Atmospheric pressure on any
given day will be around 100kPa (depending on the weather and altitude above sea level) so sitting by itself an
Absolute pressure sensor will read around 100kPa.
MAP sensors are characterized by the range of pressure they will read. In general naturally aspirated (N/A) cars
will have a 101kPa (1 bar) MAP sensor and turbo or supercharged cars will have either a 200kPa (1 bar of boost)
sensor or a 300kPa (2 bar of boost) sensor to be able to tell the ECU how much pressure above atmospheric is
being sent to the engine. It can be noted that most 1bar sensors will read a few kPa above 100 for times when
weather and altitude determine this. The placement of the MAP sensor can have a huge influence on tuning
options depending on the configuration of the engine; a N/A engine probably has the most options.
Normally Aspirated
High performance N/A engines generally have their tuning based on a Throttle Position Sensor (TPS) as the
engine load sensor. But this alone will not account for atmospheric pressure changes (changes in air temperature,
altitude and so on) so a MAP sensor can be added. The N/A engine tuner could simply add a MAP sensor to the
vehicle somewhere in the engine bay and leave the sensors vacuum port open to atmosphere and have a
fuel/ignition compensation table for the small atmospheric pressure variations.
For a N/A engine that has an idle bypass valve for idle control, a MAP sensor becomes more important. If the
tuning of the N/A engine is based on TPS the ECU will not change fueling to compensate for changes due to idle
control air bypass which results in constantly changing manifold pressure. A MAP sensor’s vacuum port must be
connected to the intake manifold plenum; MAP based fuel/ignition compensation tables (set up before tuning
begins) are then used to alter the fuel/ignition because the TPS signal is not changing while the engine is idling.
Engines with multiple throttles (throttle per cylinder) will need to have a vacuum port connection to each
cylinder on the engine side of the throttles connected to the sensor via a collector.
Forced Induction
On a turbo or super charged engine the ECU will need to know the actual pressure in the manifold plenum.
Remember once the TPS is at 100% the manifold pressure can keep rising so this is the only valid engine load
reference.
Turbo or supercharged engines will generally have their fuel and ignition tuned with reference to MAP and not TPS
although, with a MoTeC ECU it is possible to use both. I.e.: A turbo engine may be tuned on TPS with the
Wastegate disconnected so that it makes no boost and then with the Wastegate reconnected a three dimensional
Manifold Pressure table (a secondary load table) be overlaid on this to take care of fuel tuning above 100kPa. This
arrangement is generally used on engines with multiple butterflies.
Sensor Mounting
The sensor should be mounted with the vacuum port facing down and the vacuum pipe running in a continuous
downhill direction to the manifold. This will reduce the possibility of the sensor being contaminated by fuel, which
can cause sensor failure, and fuel accumulating in the pipe which can lead to in-accurate sensor readings.

 

[steino]

I bit the bullet and took her into Holden. They adjusted the IAC valve and idle. She drove like a dream for about half a tank of petrol, then started to stall all over again. Reckon I should just get my hands on a new IAC valve and chuck it in?